I'm going to show my age here I think

..
In roughly chronological order
1. Psion's Flight Simulation on the ZX Spectrum. My first ever flight sim (I was 11 or 12 years old at the time ).
2. DI's Fighter Pilot on the ZX Spectrum (my first combat sim)
3. Elite on the ZX Spectrum- never made it past 'Deadly'. Did anyone here make it to Elite?
4. F19 Stealth Fighter on the Atari ST. Played that to death..
5. Tornado - There I was perfectly happy with my Atari ST and then I played Tornado on a friends 386DX PC.. 1500 GBP later I was happy with my new 486SX, sound card, analogue Joystick and my very own copy of Tornado.
6. UFO - Enemy Unknown (X-Com on this side of the Pond)..
7. EF2000 - The second sim that I bought a new PC for... worth every penny.
8. Air Warrior III. My first online combat sim. Awesome!
9. Warbirds... Even more awesome at the time (awesome monthly bills too LOL)..
10. Company of Heroes. I never seem to get bored of it. I have the Opposing Fronts addon too.
Other notables:
Call of Duty - Like playing through the battle scenes in Band of Brothers.
MSFS 95-FSX
X-Plane 7-9
Battlefield 2
Lemmings on the ST
Homeworld 2
Knights of the Sky on the ST
Janes F15
Silent Hunter III and IV
<edit>Almost forgot IL2 1946 and F4:AF which should really be in my top 10 somewhere... oh well.